The return of the El Niño climate phenomenon later this year will cause global temperatures to rise “off the chart” and deliver unprecedented heatwaves, scientists have warned.
Early forecasts suggest El Niño will return later in 2023, exacerbating extreme weather around the globe and making it “very likely” the world will exceed 1.5C of warming. The hottest year in recorded history, 2016, was driven by a major El Niño.
It is part of a natural oscillation driven by ocean temperatures and winds in the Pacific, which switches between El Niño, its cooler counterpart La Niña, and neutral conditions. The last three years have seen an unusual run of consecutive La Niña events.
This year is already forecast to be hotter than 2022, which global datasets rank as the fifth or sixth hottest year on record. But El Niño occurs during the northern hemisphere winter and its heating effect takes months to be felt, meaning 2024 is much more likely to set a new global temperature record.
The greenhouse gases emitted by human activities have driven up average global temperature by about 1.2C to date. This has already led to catastrophic impacts around the world, from searing heatwaves in the US and Europe to devastating floods in Pakistan and Nigeria, harming millions of people.
“It’s very likely that the next big El Niño could take us over 1.5C,” said Prof Adam Scaife, the head of long-range prediction at the UK Met Office. “The probability of having the first year at 1.5C in the next five-year period is now about 50:50.”
“We know that under climate change, the impacts of El Niño events are going to get stronger, and you have to add that to the effects of climate change itself, which is growing all the time,” he said. “You put those two things together, and we are likely to see unprecedented heatwaves during the next El Niño.”
The fluctuating impacts of the El Niño-La Niña cycle could be seen in many regions of the world, Scaife said.
The scale of the likely El Niño was as yet unclear. The picture would be much clearer by June, the scientists said.
The El Niño-La Niña phenomenon is the biggest cause of year-to-year differences in weather in many regions. In La Niña years, the east-to-west Pacific trade winds are stronger, pushing warm surface waters to the west and drawing up deeper, cooler water in the east. El Niño events happen when the trade winds wane, allowing the warm waters to spread back eastwards, smothering the cooler waters and leading to a rise in global temperatures.
Nations bordering the west Pacific, including Indonesia and Australia, experience hotter and drier conditions.
India’s monsoons, and rains in southern Africa can also be suppressed. Other regions, such as east Africa and the southern US, both of which have suffered recent droughts, can get more rain and flooding. In South America, southern regions are wetter, but the Amazon, already approaching a dangerous tipping point, is drier.
